As Los Angeles-area residents were preparing for “Carmageddon II” – the second scheduled closing in two years of 10 miles of Interstate 405, the busiest highway in the country, to complete bridge work – research findings were released showing almost instantaneous improvements in air quality during the original Camageddon in July 15-17, 2011. Unfortunately, the effect was reversed soon after the freeway re-opened.

Suzanne Paulson and Yifang Zhu of UCLA published the research, which showed that air quality near the construction zone improved by 86 percent compared to comparable weekends within minutes of the road closing to passenger vehicles. And because traffic was reduced across a broad swath of the area, air quality improved up to 75 percent in parts of West Los Angeles and Santa Monica and an average of 25 percent regionally — from Ventura to Yucaipa, and Long Beach to Santa Clarita.

The pollutants measured have significant health effects. If reductions in these particles could be sustained across the entire region and consistently over time, the region could see improvements in many health problems, including asthma, heart attacks, strokes, diabetes, and low birth weights. These reductions could be possible not only by decreases in traffic overall but also by the use of more electric and other low-emission vehicles.

Even if only small reductions in traffic emissions were possible, health could be improved. “There is no safe level of PM2.5 concentrations, where you would no longer observe health impacts, so any reduction is an improvement,” notes Zhu.